Substitution balance



2 Sheets-Sheet 1 INVENTOR June 4, 1963 H. A. BQWMAN SUBSTITUTION BALANCE Filed Dec. 19, 1961 Horace A. Bowman QMA TTOPNE) ZAMGENT June 4, 1963 Y H. A. BOWMAN 3,092,193

SUBSTITUTION BALANCE Filed Dec. 19, 1961 2 Sheets-Sheet 2 IIIIIIIIZIEIIPIIIIII I 62 Fay. 7

* I 0 lh|l mm. W" 4/ |ll" .dfl MENTOR 72 7/ Horace ,4. Bowman g, 1 70 BY 75- 75 Z "22 23 ATTORNEY :the means limiting its travel.

3,092,193 SUBSTITUTION BALANCE Horace A. Bowman, Silver Spring, Md., assiguor to the United States of America as represented by the Secretary of Commerce Filed Dec. 19, 1961, Ser. No. 160,68t) 13 Claims. ((31. 177-151) This invention relates to a substitution balance and more particularly relates to a substitution balance having an improved arrestment mechanism.

The term substitution balance as used herein refers to a balance of the type employing a pivoted balance beam having at one end a counterweight, and at the other end a pan assembly for holding both a mass to be weighed and a set of weights of known value. Such a balance is also referred to in the art as a single pan balance.

Prior substitution balances have been provided with a cradle-like member for bringing the beam into arrestment. The cradle member is disposed beneath the beam and is moved upward under the control of the operator of the substitution balance. As the cradle member is moved upward, pins projecting from the cradle contact the pan assembly and lift it from the associated knife, commonly designated as the terminal knife. The cradle member is further moved upward until additional pins projecting from the cradle come into contact with the beam and lift it from the associated or center knife. With the cradle thus holding the pan assembly from the terminal knife and the beam from the center bearing, the pan may be loaded or unloaded without damaging the terminal and center knives. The cradle, of course, is lowered by the operator to perform a weighing. It will be readily appreciated that the cradle mechanism should lower the knives onto their designed lines of contact on their associated bearing surfaces or flats. To this end, such prior cradle mechanisms have been fitted into carefully constructed guideways. The cradle mechanisms of prior balances in consequence have been costly, complicated, and the source of substantial error in replacing the knives on their designed lines of con-tact.

In accordance with the present invention, means are knife or load end of the beam. The beam may be rotated by an external member or by the addition of weights to the pan assembly. In another embodiment of the present invention, further pins in addition to those described above are provided. These pins are also attached to the base and are arranged to contact lateral projections from the beam, whereby additional rotation of the beam in a direction to lower the terminal knife or load end of the beam causes the lateral projections to contact the further pins, the center knife as a result being lifted from its bearing or fiat. In a further embodiment of the invention, means are provided to block upward motion of the pan assembly, and the beam is rota-ted in a direction to raise the pan assembly causing the pan assembly to contact the blocking means. It has been found that the knives become stressed in such a manner that the pan may be loaded or unloaded without noticeable damage to the knives.

In all of the above embodiments of the invention, the arrestment is achieved by the provision of fixed rigid means'that limit the travel of the pan in combination with means for rotating the beam until the pan contacts By such combination of .holes 24 and 25 provided therein.

3,l 2,l93 Patented June 4, 1963 means, the need for a movable, external cradle is avoided, and as a, result the error in locating the knives on their designed lines of contact that is inherent in movable cradle means is avoided. In addition, the necessity of costly cradle guideways is avoided.

It is accordingly an object of this invention to provide a substitution balance wherein the motion that effects arrestment is imparted to the beam, rather than to a cradle fitted in-to guideways.

Another object is to provide a substitution balance wherein the pan is held by fixed means while the beam is rotated free thereof.

A further object of the present invention is to provide a substitution balance wherein the knives are separated from their associated flats by rotation of the beam.

Still another object is to provide a substitution balance wherein the knives thereof are always seated on the designed lines of contact after arrestment.

A final object of this invention is to provide a subs-titution balance that is arrested by a fixed-pin mechanism.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes bett'er understood by reference to the following detailed description when considered in connection with .the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein:

FIG. 1 is a perspective view of a preferred embodiment of the invent-ion;

FIG. 2 is a side view of the structure illustrated in FIG. 3 is a side view of the structure illustrated in FIG. 1 as it appears when the terminal knife is arrested;

FIG. 4'is a side view of a modification of the structure illustrated in FIG. 1;

FIG. 5 is a side view of another modification of the structure illustrated in FIG. 1 when both knives are arrested; i

FIG.'6 is a view taken along line 6-6 of the device illustrated'in FIG. 5, and,

FIG. 7 is a side view of another embodiment of the invention.

The substitution balance shown in FIGS. 1 to 3 has a base 11 to which is attached an upright column 12. The top of column '12 is provided with a bearing surface or fiat 13 for the center knife 14 that is carried by balance beam 15, all in accordance with well-known practices. Attached to the right-hand end of balance beam 15 is a counterweight 16, which may be of any convenient construction. The counterweight 16 may be made an integral part of the beam or it may be made removable to accommodate counterweights of different sizes and/or materials. The left-hand end of balance beam 15 carries a terminal or .end knife 17. For precision weighings, terminal knife 17 and the center of counterweight 16 preferably are disposed at equal distances from the center knife 14, although they may be located at unequal distances from the center knife 14 to suit other applications.

The terminal knife 17 normally engages a bearing plate or flat 20 to which are attached suspension means such as rods 21 and 22 for holding pan 23. The suspension rods 21 and 22 extend through base 11 by means of Pan 23 holds the mass to be weighed and a set of weights of known value and project therefrom towards the ends of fiat 2.0. The

pins 33 and 34 may be attached to base 11 by any convenient means (not shown), for example, by being threaded into base 11 and locked with lock nuts, by

brazing, or the like. Pins 33, 34 extend vertically upwards from base 11 a distance slightly less than the distance between base 11 and the ends of flat 21 as measured when the beam 15 is in the balance position, usually near horizontal. Thus, when the left-hand or load end of beam 15 is rotated in a downward direction from the balance position, the flat 20 rests on pins 33 and 34, and the terminal knife 17 becomes separated from the flat 20 as shown in FIG. 3.

In FIGS. 1 to 3, the means to rotate the left-hand or load end of beam 15 in the downward direction comprises a lifting device 40 adapted to lift the right-hand or counterweight end of the beam 15. The lifting device 40 has a rod 41 slidably fitted into a bearing 42 provided in base 11. The tip of rod 41 preferably is fitted with a ball 43 that is free to roll. The purpose of the rolling ball 43 is to exert a lifting force on projection 18 of beam 15 with a minimum of lateral force that would tend to cause center knife 14 to move across center flat 13. The rod 41 is of course under the control of the operator, and may be actuated by any convenient means (not shown), for example, by means of a cam device connected to a knob on the front of a housing that encloses the complete scale mechanism.

In FIG. 4, there is shown an alternative means for lowering the load end of beam 15, which comprises a weight W placed on the pan assembly. The weight W may be applied to fiat 20, for example, by any convenient means. It will readily be appreciated that the addition of such a weight W to the pan assembly will cause the load end of beam 15 to swing below the normal or near balance position, and cause flat 20 to rest on pins 33, 34. Since the flat is then primarily supported by pins 33, 34, and is secondarily supported by terminal knife 17, the pan assembly that hangs from flat 20 clearly can be loaded or unloaded without damaging the terminal knife 17, inasmuch as any shock associated with loading and unloading is substantially absorbed by pins 33, '34 that are rigidly attached to base 11. When employing such a weight W to rotate the beam, no external lift means, such as were illustrated in connection with FIGS. 1 to 3, are necessary, although lifting means may be provided to cause flat 20 to contact pins 33, 34 before applying weight W. It is contemplated that further means for rotating beam 15 in a direction to lower the load end, so that flat 2t rests on pins 33, 34, will be apparent to those skilled in the art, and it is intended that any such means may be employed when desired within the scope of the invention.

For many weighing operations, the above described arrestment of terminal knife 17 from flat 20 by rotation of beam 15 to cause flat 20 to rest on fixed pins 33, 34 will sufiice. However, where it is desired to additionally separate center knife 14- from its associated flat 13, the means illustrated in FIGS. 5 and 6 may be provided. In FIGS. 5 and 6, beam 15 is provided with lateral extensions 51 and 52 projecting from opposite sides of beam 15, as best seen in FIG. 6 The lateral extension 51, 52 are positioned on opposite sides of beam 15 along the portion of beam 15 between center knife 14 and terminal knife 17. Positioned to cooperate with the lateral extensions 51, 52 in effecting separation of center knife 14 from flat 13, are pins '56, 57 which are rigidly attached to base 11 in the manner described with reference to pins 33 and 34. The pins 56, 57 project upwardly from base 11 towards lateral extensions 51, 52, a distance which is slightly less than the distance from base 11 to lateral extensions 51, 52 as measured when the beam is substantially balanced or approximately horizontal. when the beam is rotated in the direction to lower the Consequently,

pins 33, 34 should be such that initial rotation of the beam 15 from the balance position in the direction to lower the load end causes fiat 211 to contact pins 33 and 34, and additional rotation causes lateral extensions 51, 52 to contact pins 56, 57. The rotation may, of course, be efiected by lifting device 49-, previously described. Since the function of pins 56, 57 is to provide a substitute pivot for center knife 14, the line connecting their centers is parallel to the line defined by the edge of center knife 14, and as close to center knife 14 as is convenient.

The lower surfaces of lateral extensions 51, 5'2 pivot on pins 56 and 57, and consequently it may be desirable to shape these surfaces to preclude slippage of the surfaces across pins 56 and 57. For example, the undersides of each of the lateral extensions 51, 52 may be provided with a V-shaped depression as illustrated at 58 in FIG. 5, which depressions are adapted to align with the points of pins 56 and 57, respectively.

In FIG. 7, another embodiment of the present invention is illustrated, wherein upward travel of pan 23 is limited by means of a blocking device 70. The device consists of a flange 71 attached to the underside of base 11. Horizontally disposed through flange 71 is a rod 73 that may be made retractable, if desired, by the provision of a suitable bearing 72. The rod 73- is provided to cooperate with a cross bar connected between the suspension rods 21 and 22 (see FIG. 1) that support the pan 23. The cross bar 75 is located along the lengths of rods 21 and 22 at a distance below base 11 that is slightly greater than the distance between base 11 and rod 73, the measurement along rods 21 and 22 being made when the beam 15 is in the balanced position. Thus when the load end of beam 15 is raised above the balance position, cross bar 75 moves upward until it is stopped by rod 73. As a result, terminal knife 17 is held in firm engagement with terminal flat 2t), and center knife 14 is held firmly in contact with center flat 13. Such firm contact between the knives and flats places heavy constant stress upon the knives, which condition, it has been discovered, enables the knives to withstand the shock associated with loading and unloading of pan 23.

To raise the load end of beam 15, the device 60 is provided to pull down on the counterweight end 19 of the beam 15. The device 60 consists of a hook-shaped member 61 slidably disposed in a bearing 62 provided in base 11. The end of hook-shaped member 61 is fitted with a rolling ball 63, similar to the rolling ball 43 described in connection with the balance illustrated in FIGS. 1 to 3. The member 61 is under the control of the operator and may be actuated by the suspension of a weight thereon. The use of a Weight to pull 61 down insures that the knives 14-, 17 are properly stressed. As an alternative, rod 73 may be made of spring material, and member 61 may be pulled down by hand until rod 73 of spring material deflects a desired amount.

If desired, the pull-down device 60 illustrated in FIG. 7 may be omitted, and the beam 15 may be rotated in the direction to raise the load end simply by lifting the weight or load on pan 23. It will be readily apparent that when the load is removed from pan 23, the beam 15 rotates under the influence of counterweight 16, cansing cross-bar 75 to come into contact with blocking rod 73, thereby achieving arrestment of the beam 15. Any convenient means for lifting the load from pan 23 may be employed. An exemplary means consists of the wellknown finger-shaped arrangement employed in conjunction with a multi-bar pan for placing and removing loads from the pan, such as is illustrated in FIG. 79 (page 179) of Feine Waagen, Wagungen und Gewichte by Felgentraeger, published in 1932 by Springer of Berlin. It is contemplated that various means for stressing the center and terminal knives in the described manner will be apparent to those skilled in the art, and it is intended that any such means may be employed when desired.

In all of the above exemplary embodiments of the invention, the balance has been illustrated as having a single terminal knife 17 and fiat 20, with a pan 23 suspended directly from the flat 20. To achieve high precision, it may be desirable to attach pan 23 not to flat 20, but rather to another downwardly-directed knife that engages another fiat disposed on fiat 20, the longitudinal axis of the further flat being at right angles with the longitudinal axis of the flat 20. Those skilled in the art Will recognize such further knife and fiat as comprising the well-known intermediate" knife structure. It will readily be appreciated that when such intermediate structure is employed, the fixed pins 33, 34 may be disposed to support either of the flats, as desired.

While the present embodiment has been illustrated with specific exemplary embodiments, it is to be understood that those skilled in the art may embody the invention with variations which are well within the spirit and scope of the invention, and it is not intended to be limited except as set forth in the following claims.

What is claimed is:

l. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, base means upon which said center knife pivots, a pan assembly suspended from a flat associated with said terminal knife, and means for arresting said beam, said arresting means comprising means rigidly attached to said base means for limiting the travel of said pan assembly, and means for rotating said beam until said pan assembly contacts said means for limiting its travel.

2. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, base means upon which said center knife pivots, a pan suspended from a fiat associated with said terminal knife, and means for arresting said beam, said arresting means comprising pin members rigidly fixed to said base means and extending upward toward said flat from which said pan is suspended, and means for rotating said beam in a direction to lower said terminal knife, whereby said flat is lowered onto said members and said terminal knife is separated from said flat.

3. A substitution balance as set forth in claim 2, where'- in said means for rotating said beam in a direction to lower said terminal knife comprises a rod for lifting the counterweight end of said beam, said rod being slidably fitted into a bearing in said base means beneath said counterweight end of said beam.

4. A substitution balance as set forth in claim 3, wherein the tip of said rod is provided with rolling means.

5. A substitution balance as set forth in claim 2, wherein said means for rotating said beam in the direction to lower said terminal knife comprises a weight, said weight being placed on said fiat whereby said pan is lowered onto said pin members.

6. A substitution balance as set forth in claim 2, and further having means for lifting said center knife comprising lateral extensions on said beam located between said center knife and said terminal knife, further pin members rigidly fixed to said base means and extending upward towards said lateral extensions, whereby said lateral extensions rest on said further pin members and cause the beam to pivot thereon as said beam is rotated in the direction to lower the terminal knife.

7. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, base means upon which said center knife pivots, a pan suspended from a fiat associated with said terminal knife, and means for arresting said beam, said arresting means comprising an arm member attached to said base means and projecting toward said pan, a stop member attached to said pan beneath said projecting arm member, and means for rotating said beam in the direction to raise said terminal knife, whereby said stop member contacts said arm member and causes said center and terminal knives to become stressed.

8. A substitution balance comprising a base, an upright column attached to said base, the top of said column having a bearing surface, a beam, said beam having a downwardly directed center knife disposed on the central portion thereof and further having a terminal knife and counterweight disposed at the ends thereof, said center knife being pivoted on said bearing surface, a terminal fiat engaging said terminal knife, said terminal fiat having ends projecting beyond said terminal knife, a pan suspended from said terminal flat, and means for separating said terminal and center knives from said terminal flat and bearing surface, respectively, said separating means comprising a plurality of pins rigidly attached to said base beneath said projecting ends of said terminal flat, said plurality of pins being slightly shorter than the distance from the base to the under side of said terminal flat as measured when said beam is in the balanced position, a pair of lateral extensions disposed on opposite sides of said beam along the portion between said center and terminal knives, a pair of pins rigidly attached to said base beneath said pair of lateral extensions, said pair of pins being slightly shorter than the distance from said base to the undersides of said pair of lateral extensions as measured when said beam is in the balanced position, and means to rotate said beam in the direction to lower said terminal knife.

9. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, a base, a bearing surface attached to said base, said center knife being pivoted on said bearing surface, a pan, suspension means for suspending said pan from said terminal knife, and means for arresting said beam, said arresting means comprising means rigidly attached to said base for limiting the travel of said suspension means, and means for rotating said beam until said suspension means contacts said limiting means.

10. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, a base, a bearing surface attached to said base, said center knife being pivoted on said bearing surface, a pan, suspension means for suspending said pan from said terminal knife, and means for arresting said beam, said arresting means comprising means fixed relative to said bearing surface for limiting the travel of said suspension means, and means for rotating said beam until said suspension means contacts said limiting means.

11. A substitution balance comprising a beam having a center knife, 9. terminal knife, and a counterweight, a base, a bearing surface attached to said base, said center knife being pivoted on said bearing surface, a pan, suspension means for suspending said pan from said terminal knife, and means for arresting said beam, said arresting means comprising pin members rigidly attached to said base for supporting said suspension means when said beam is rotated so as to lower said terminal knife, and means for rotating said beam in the direction to lower said terminal knife.

12. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, a base, a bearing surface attached to said base, said center knife being pivoted on said bearing surface, a pan, suspension means for suspending said pan from said terminal knife, and means for arresting said beam, said arresting means comprising pin members fixed with respect to said bearing surface for supporting said suspension means when said beam is rotated so as to lower said terminal knife, and means for rotating said beam in the direction to lower said terminal knife.

13. A substitution balance comprising a beam having a center knife, a terminal knife, and a counterweight, a base, a bearing surface attached to said base, said center knife being pivoted on said bearing surface, a pan,

suspension means for suspending said pan from said terminal knife, and means for arresting said beam, said arresting means comprising arm means attached to said base and projecting towards said suspension means, stop 7 3,092,193 7 8 means attached to said-suspension means and coopera-ble References fit ed in the file of this patent with said arm means ,for blocking upward motion of UNITED STATES PATENTS said suspension means, and means for rotating said beam in the direction to raise said suspension means so that 2,581,307 Me r fit 1952 said step means contacts said arm means, causing said 5 3,029,882 Kriznic Apr. 17, 1962 center and terminal knives to become stressed. 3,039,549 Meier June 19, 1962 

1. A SUBSTITUTION BALANCE COMPRISING A BEAM HAVING A CENTER KNIFE, A TERMINAL KNIFE, AND A COUNTERWEIGHT, BASE MEANS UPON WHICH SAID CENTER KNIFE PIVOTS, A PAN ASSEMBLY SUSPENDED FROM A FLAT ASSOCIATED WITH SAID TERMINAL KNIFE, AND MEANS FOR ARRESTING SAID BEAM, SAID ARRESTING MEANS COMPRISING MEANS RIGIDLY ATTACHED TO SAID BASE MEANS FOR LIMITING THE TRAVEL OF SAID PAN ASSEMBLY, AND MEANS FOR ROTATING SAID BEAM UNTIL SAID PAN ASSEMBLY CONTACTS SAID MEANS FOR LIMITING ITS TRAVEL. 